Dual-element substitution induced integrated defect structure to suppress voltage decay and capacity fading of Li-rich Mn-based cathode

Figure. Dual-element substitution induced integrated defect structure to suppress voltage decay and capacity fading of Li-rich Mn-based cathode. [Display omitted] •The integrated defects are constructed in Li-rich cathodes by Na2SnO3 modification.•The modification improves the cycling stability and suppresses the voltage decay.•The mechanism of enhanced performance by Na2SnO3 modification is revealed. Li-rich manganese-based oxide (LRMO) is considered one of the most promising cathode materials for next-generation lithium-ion batteries due to its high energy density. However, many issues need to be addressed before its large-scale commercialization, including significant voltage decay and capacity fading. Herein, a Sn4+/Na+ co-doping induced integrated defect structure (oxygen vacancies, stacking faults, and surface spinel phase) strategy is proposed to suppress the voltage decay and enhance the cycling performance of LRMO. The integrated surface defect structures have significantly favorable effects on the LRMO, where the oxygen vacancies remove surface labile oxygen and suppress surface oxygen release, the induced stacking faults alleviate the stress accumulation during cycling, the surface spinel phase promotes the Li+ diffusion and prevents the outward migration of cations, and the co-doped Sn4+/Na+ stabilize the layered structure. As a result, the modified sample Na2SnO3-1 % (NSO-1) achieves excellent cycling performance (capacity of 207 mAh/g and capacity retention of 96.71 % after 100 cycles at 0.5C) and a smaller voltage decay (less than 1.5 mV per cycle) compared with the unmodified LRMO. This work provides a new valuable strategy to suppress capacity fading and voltage decay of LRMO through dual-element substitution induced surface defect engineering.